Fate of enterohemorrhagic Escherichia coli O157:H7 in bovine feces

Biological soil amendments can support survival of pathogenic and non-pathogenic Escherichia coli in soils and sporadic transfer to Romaine lettuce

Biological soil amendments (BSAs) are essential agricultural inputs that provide critical nutrients in organic leafy green production. Heat-treated poultry pellets (HTPP) and seabird guano (SBG), which have been treated to reduce microbial pathogen loads, are gaining popularity among growers. Using these BSAs in the process of side-dressing, providing nutrients to crops while growing, may provide opportunities for externally introduced bacterial pathogens to survive in soil. In this study, Romaine lettuce was grown in soils in a controlled environmental growth chamber. Soils were side-dressed twice with different combinations of treated BSAs: HTPP, SBG, and corn steep liquor (CSL). Soils were co-inoculated with non-pathogenic E. coli and two E. coli O157:H7 strains at the second of two side-dressing events. Survival of E. coli in soils over 28 days was evaluated. On day 28 post inoculation, two heads of Romaine lettuce from each planter were harvested, and the presence of E. coli on leaves was determined. Four nonlinear statistical models were fit to predict survival of E. coli in soils. In all soils regardless of BSA treatment, E. coli TVS 353 declined by 4.08-4.51 log CFU/g soil over 28 days, and E. coli O157:H7 declined by 2.77-4.3 log CFU/g soil over 28 days. E. coli TVS 353 and O157:H7 were recovered from 13.3 % (6/45) and 11.1 % (5/45) of plants, respectively. Transfer of E. coli from soils to Romaine lettuce was low, sporadic, and could not be measured quantitatively. Side-dressing with treated BSAs used in organic lettuce production supported but did not enhance survival of E. coli in side-dressed soils under controlled environmental conditions.

Prevention of foodborne viruses and pathogens in fresh produce and root vegetables

Every year, 1 in 10 people suffers from food poisoning, and in recent years, the highest number of foodborne outbreaks has been attributed to roots/underground vegetables and fresh produce. Major pathogens include as Escherichia coli, Salmonella enterica, Listeria monocytogenes, Human Norovirus, Hepatitis A virus and Cyclospora. The primary sources of contamination for agriculture products stem from uncontrolled exposure to soil, water, and animal waste. Contamination can occur in various ways during food cultivation, harvesting, processing, and distribution. Mechanical washing and disinfection are primarily employed as practices to control biological contaminants such as bacteria, viruses, and parasites. Current practices may encounter challenges such as microbial resistance to disinfectants or antibiotics, and the cleaning effectiveness could be compromised due to the internalization of bacteria and viruses into some plants. High-pressure processing, pulse electric fields, and cold plasma are environmentally friendly technologies, albeit with associated costs. Low-temperature sterilization technologies capable of controlling biological contaminants, such as bacteria and viruses, play a crucial role in preventing food safety issues. Compared to conventional cleaning methods, these technologies are effective in controlling microorganisms that are strongly attached to the food surface or internalized due to damage. Periodic surveillance is essential to ensure the overall microbiological safety of fresh produce and root vegetables.

Cold-tolerance mechanisms in foodborne pathogens: Escherichia coli and Listeria monocytogenes as examples

The cold chain is an integral part of the modern food industry. Low temperatures can effectively alleviate food loss and the transmission of foodborne diseases caused by microbial reproduction. However, recent reports have highlighted shortcomings in the current cold chain technology's ability to prevent and control cold-tolerant foodborne pathogens. Furthermore, it has been observed that certain cold-chain foods have emerged as new sources of infection for foodborne disease outbreaks. Consequently, there is a pressing need to enhance control measures targeting cold-tolerant pathogens within the existing cold chain system. This paper aims to review the recent advancements in understanding the cold tolerance mechanisms of key model organisms, identify key issues in current research, and explore the potential of utilizing big data and omics technology in future studies.

Detection of multidrug-resistant Shiga toxin-producing Escherichia coli in some food products and cattle faeces in Al-Sharkia, Egypt: one health menace

BACKGROUND

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathogen, that is transmitted from a variety of animals, especially cattle to humans via contaminated food, water, feaces or contact with infected environment or animals. The ability of STEC strains to cause gastrointestinal complications in human is due to the production of Shiga toxins (sxt). However, the transmission of multidrug-resistance STEC strains are linked with a severity of disease outcomes and horizontal spread of resistance genes in other pathogens. The result of this has emerged as a significant threat to public health, animal health, food safety, and the environment. Therefore, the purpose of this study is to investigate the antibiogram profile of enteric E. coli O157 isolated from food products and cattle faeces samples in Zagazig City, Al-Sharkia, Egypt, and to reveal the presence of Shiga toxin genes stx1 and stx2 as virulence factors in multidrug-resistant isolates. In addition to this, the partial 16S rRNA sequencing was used for the identification and genetic recoding of the obtained STEC isolates.

RESULTS

There was a total of sixty-five samples collected from different geographical regions at Zagazig City, Al-Sharkia-Egypt, which were divided into: 15 chicken meat (C), 10 luncheon (L), 10 hamburgers (H), and 30 cattle faeces (CF). From the sixty-five samples, only 10 samples (one from H, and 9 from CF) were identified as suspicious E. coli O157 with colourless colonies on sorbitol MacConkey agar media with Cefixime- Telurite supplement at the last step of most probable number (MPN) technique. Eight isolates (all from CF) were identified as multidrug-resistant (MDR) as they showed resistance to three antibiotics with multiple antibiotic resistance (MAR) index ≥ 0.23, which were assessed by standard Kirby-Bauer disc diffusion method. These eight isolates demonstrated complete resistance (100%) against amoxicillin/clavulanic acid, and high frequencies of resistance (90%, 70%, 60%,60%, and 40%) against cefoxitin, polymixin, erythromycin, ceftazidime, and piperacillin, respectively. Those eight MDR E. coli O157 underwent serological assay to confirm their serotype. Only two isolates (CF8, and CF13), both from CF, were showed strong agglutination with antisera O157 and H7, as well as resistance against 8 out of 13 of the used antibiotics with the highest MAR index (0.62). The presence of virulence genes Shiga toxins (stx1 and stx2) was assessed by PCR technique. CF8 was confirmed for carrying stx2, while CF13 was carrying both genes stx1, and stx2. Both isolates were identified by partial molecular 16S rRNA sequencing and have an accession number (Acc. No.) of LC666912, and LC666913 on gene bank. Phylogenetic analysis showed that CF8, and CF13 were highly homologous (98%) to E. coli H7 strain, and (100%) to E. coli DH7, respectively.

CONCLUSION

The results of this study provides evidence for the occurrence of E. coli O157:H7 that carries Shiga toxins stx1 and/or stx2, with a high frequency of resistance to antibiotics commonly used in human and veterinary medicine, in Zagazig City, Al-Sharkia, Egypt. This has a high extent of public health risk posed by animal reservoirs and food products with respect to easy transmission causing outbreaks and transfer resistance genes to other pathogens in animal, human, and plants. Therefore, environmental, animal husbandry, and food product surveillance, as well as, clinical infection control, must be strengthened to avoid the extra spread of MDR pathogens, especially MDR STEC strains.

Diarrheagenic Escherichia coli and Their Antibiotic Resistance Patterns in Dairy Farms and Their Microbial Ecosystems

Ruminants are the largest reservoir for all types of Escherichia coli, including the pathogenic ones, which can potentially be transmitted to humans via the food chain and environment. A longitudinal study was performed to estimate the prevalence and antibiotic-resistant pattern of pathogenic E. coli (pE.coli) strains in dairy farm environments. A total of 846 environmental samples (water, lagoon slurry, bedding, feed, feces, soil, and compost) were collected in summer over two years from five dairy farms in Maryland, USA. An additional 40 soil samples were collected in winter and summer seasons for evaluating microbiome composition. Collected environmental samples were screened for the presence of pE.coli, which was isolated using a selective culture medium, for later confirmation and virotyping using PCR with specific primers. The overall prevalence of pE.coli in dairy farms was 8.93% (71/846), with the most common virotype identified in isolates being ETEC, followed by STEC. The highest pE.coli prevalence were recorded in lagoon slurry (21.57%) while the lowest was in compost heap (2.99%). Among isolates, 95.87% of the virotypes were resistant to 9 classes of antibiotics whereas only 4.12% were sensitive. The highest proportion (68.04%) of resistance was found for quinolones (e.g., ciprofloxacin). The resulting metagenomic analysis at the phylum and genus levels of the grazing land soil suggests that climatic conditions actively influence the abundance of bacteria. Proteobacteria, which contains many Gram-negative foodborne pathogens (including pE.coli), was the most predominant phylum, accounting for 26.70% and 24.93% of soil bacteria in summer and winter, respectively. In addition to relative abundance, there was no significant difference in species diversity between seasons when calculated via Simpson (D) and Shannon (H) index. This study suggests that antibiotic-resistant E. coli virotypes are present in the dairy farm environment, and proper steps are warranted to control its transmission irrespective of seasonality.

The Fate of Foodborne Pathogens in Manure Treated Soil

The aim of this review was to provide an update on the complex relationship between manure application, altered pathogen levels and antibiotic resistance. This is necessary to protect health and improve the sustainability of this major farming practice in agricultural systems based on high levels of manure production. It is important to consider soil health in relation to environment and land management practices in the context of the soil microflora and the introduction of pathogens on the health of the soil microbiome. Viable pathogens in manure spread on agricultural land may be distributed by leaching, surface run-off, water source contamination and contaminated crop removal. Thus it is important to understand how multiple pathogens can persist in manures and on soil at farm-scale and how crops produced under these conditions could be a potential transfer route for zoonotic pathogens. The management of pathogen load within livestock manure is a potential mechanism for the reduction and prevention of outbreaks infection with Escherichia coli, Listeria Salmonella, and Campylobacter. The ability of Campylobacter, E. coli, Listeria and Salmonella to combat environmental stress coupled with their survival on food crops and vegetables post-harvest emphasizes the need for further study of these pathogens along with the emerging pathogen Providencia given its link to disease in the immunocompromised and its’ high levels of antibiotic resistance. The management of pathogen load within livestock manure has been widely recognized as a potential mechanism for the reduction and prevention of outbreaks infection but any studies undertaken should be considered as region specific due to the variable nature of the factors influencing pathogen content and survival in manures and soil. Mediocre soils that require nutrients could be one template for research on manure inputs and their influence on soil health and on pathogen survival on grassland and in food crops.

Improving the Properties of Degraded Soils from Industrial Areas by Using Livestock Waste with Calcium Peroxide as a Green Oxidizer

Over the past years, the treatment and use of livestock waste has posed a significant problem in environmental engineering. This paper outlines a new approach to application of calcium peroxide (CaO₂) as a green oxidizer and microbiocidal agent in the treatment of poultry manure. It also presents the application of pretreated waste in improvement of degraded soils in industrial areas. The CCD (Central Composite Design) and RSM (Response Surface Methodology) were employed for optimizing the process parameters (CaO₂ concentration 1.6–8.4 wt %, temperature 5.2–38.8 °C and contact time 7–209 h). The analysis of variance (ANOVA) was used to analyze the experimental results, which indicated good fit of the approximated to the experimental data (R² = 0.8901, R²_adj = 0.8168). The amendment of CaO₂ in optimal conditions (8 wt % of CaO_2, temperature 22 °C and contact time 108 h) caused a decrease in bacteria Escherichia coli (E. coli) in poultry manure from 8.7 log₁₀ CFU/g to the acceptable level of 3 log₁₀ CFU/g. The application of pretreated livestock waste on degraded soils and the studies on germination and growth of grass seed mixture (Lollum perenne—Naki, Lollum perenne—Grilla, Poa pratensis—Oxford, Festuca rubbra—Relevant, Festuca rubbra—Adio and Festuca trachypylla—Fornito) showed that a dose of 0.08 g of CaO₂ per 1 gram of poultry manure induced higher yield of grass plants. The calculated indicators for growth of roots (GFR) and shoots (GFS) in soils treated with poultry manure were 10–20% lower compared to soils with amended CaO₂. The evidence from this study suggests that CaO₂ could be used as an environmentally friendly oxidizer and microbiocidal agent for livestock waste.

Shiga Toxin-Producing E. coli in Animals: Detection, Characterization, and Virulence Assessment

Cattle and other ruminants are primary reservoirs for Shiga toxin-producing Escherichia coli (STEC) strains which have a highly variable, but unpredictable, pathogenic potential for humans. Domestic swine can carry and shed STEC, but only STEC strains producing the Shiga toxin (Stx) 2e variant and causing edema disease in piglets are considered pathogens of veterinary medical interest. In this chapter, we present general diagnostic workflows for sampling livestock animals to assess STEC prevalence, magnitude, and duration of host colonization. This is followed by detailed method protocols for STEC detection and typing at genetic and phenotypic levels to assess the relative virulence exerted by the strains.

Occurrence of 'gang of five' Shiga toxin-producing Escherichia coli serogroups on Belgian dairy cattle farms by overshoe sampling

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens responsible for global outbreaks. This study was conducted to investigate the occurrence of 'gang of five' STEC serogroups (O26, O103, O111, O145, O157) on Belgian dairy cattle farms by overshoe (OVS) sampling, and to evaluate the presence of virulence genes in the obtained isolates. A total of 88 OVS, collected from the pen beddings of 19 Belgian dairy cattle farms, were selectively enriched in mTSBn, followed by immunomagnetic separation and plating onto CT-SMAC for O157 STEC isolation, as well as in Brila broth, followed by a selective acid treatment and plating onto CHROMagar^TM STEC and chromID^TM EHEC for non-O157 STEC isolation. Overall, 11 of 19 farms (58%) tested positive for presence of 'gang of five' STEC. O26 STEC was most frequently isolated from OVS (11/88; 12·5%), followed by O157 (10/88; 11·5%), O145 (3/88; 3·5%) and O103 (3/88; 3·5%). Additionally, 35% of the OVS collected from pens housing young cattle 1-24 months of age tested positive for 'gang of five' STEC, indicating that this age category is more likely to harbour STEC compared to new-born and adult cattle. Importantly, half of the obtained 'gang of five' STEC isolates (48%) possessed the eae and stx2 gene, suggesting a high pathogenic potential to humans.

Survival of Shiga Toxin-Producing Escherichia coli in Various Wild Animal Feces That May Contaminate Produce

ABSTRACT

Domestic and wild animal intrusions are identified as a food safety risk during fresh produce production. The purpose of this study was to evaluate the survival of Shiga toxin-producing Escherichia coli (STEC) in cattle, feral pig, waterfowl, deer, and raccoon feces from sources in California, Delaware, Florida, and Ohio. Fecal samples were inoculated with a cocktail of rifampin-resistant STEC serotypes (O103, O104, O111, O145, and O157) (104 to 106 CFU/g of feces). Inoculated feces were held at ambient temperature. Populations of surviving cells were monitored throughout 1 year (364 days), with viable populations being enumerated by spread plating and enrichment when the bacteria were no longer detected by plating. Representative colonies were collected at various time intervals based on availability from different locations to determine the persistence of surviving STEC serotypes. Over the 364-day storage period, similar survival trends were observed for each type of animal feces from all states except for cattle and deer feces from Ohio. STEC populations remained the highest in cattle and deer feces from all states between days 28 and 364, except for those from Ohio. Feral pig, waterfowl, and raccoon feces had populations of STEC of <1.0 log CFU/g starting from day 112 in feces from all states. E. coli O103 and O104 were the predominant serotypes throughout the entire storage period in feces from all animals and from all states. The survival of both O157 and non-O157 STEC strains in domesticated and wild animal feces indicates a potential risk of contamination from animal intrusion.

HIGHLIGHTS

An Overview of the Elusive Passenger in the Gastrointestinal Tract of Cattle: The Shiga Toxin Producing Escherichia coli

For approximately 10,000 years, cattle have been our major source of meat and dairy. However, cattle are also a major reservoir for dangerous foodborne pathogens that belong to the Shiga toxin-producing Escherichia coli (STEC) group. Even though STEC infections in humans are rare, they are often lethal, as treatment options are limited. In cattle, STEC infections are typically asymptomatic and STEC is able to survive and persist in the cattle GIT by escaping the immune defenses of the host. Interactions with members of the native gut microbiota can favor or inhibit its persistence in cattle, but research in this direction is still in its infancy. Diet, temperature and season but also industrialized animal husbandry practices have a profound effect on STEC prevalence and the native gut microbiota composition. Thus, exploring the native cattle gut microbiota in depth, its interactions with STEC and the factors that affect them could offer viable solutions against STEC carriage in cattle.

Survival of Salmonella in Various Wild Animal Feces That May Contaminate Produce

ABSTRACT

Heightened concerns about wildlife on produce farms and possible introduction of pathogens to the food supply have resulted in required actions following intrusion events. The purpose of this study was to evaluate the survival of Salmonella in feces from cattle and various wild animals (feral pigs, waterfowl, deer, and raccoons) in California, Delaware, Florida, and Ohio. Feces were inoculated with rifampin-resistant Salmonella enterica cocktails that included six serotypes: Typhimurium, Montevideo, Anatum, Javiana, Braenderup, and Newport (104 to 106 CFU/g). Fecal samples were stored at ambient temperature. Populations were enumerated for up to 1 year (364 days) by spread plating onto tryptic soy agar supplemented with rifampin. When no colonies were detected, samples were enriched. Colonies were banked on various sampling days based on availability of serotyping in each state. During the 364-day storage period, Salmonella populations decreased to ≤2.0 log CFU/g by day 84 in pig, waterfowl, and raccoon feces from all states. Salmonella populations in cattle and deer feces were 3.3 to 6.1 log CFU/g on day 336 or 364; however, in Ohio Salmonella was not detected after 120 days. Salmonella serotypes Anatum, Braenderup, and Javiana were the predominant serotypes throughout the storage period in all animal feces and states. Determination of appropriate risk mitigation strategies following animal intrusions can improve our understanding of pathogen survival in animal feces.

HIGHLIGHTS

Pathogen Reduction Potential in Anaerobic Digestion of Organic Fraction of Municipal Solid Waste and Food Waste

Anaerobic digestion (AD) is a commonly used method of processing waste. Regardless of the type of the used digestate (fertilizer, feedstock in case of solid-state fermentation, raw-material in case of thermal treatment) effective pathogen risk elimination, even in the case of high pathogen concentration is essential. An investigation of the survival time and inactivation rate of the Salmonella Senftenberg W₇₇₅, Enterococcus spp., and Ascaris suum eggs during thermophilic anaerobic digestion performed on laboratory scale and confirmation of hygienization in full-scale operation were performed in this study. Except for sanitization efficiency, the AD process performance and stability were also verified based on determination of pH value, dry matter content, acidity, alkalinity, and content of fatty acids. The elimination of pathogen was met within 6.06 h, 5.5 h, and about 10 h for the Salmonella Senftenberg W₇₇₅, Enterococcus spp., and Ascaris suum, respectively in the laboratory trials. The obtained results were confirmed in full-scale tests, using 1500 m³ Kompogas^® reactors, operating in MBT Plant located in Poland. Sanitization of the digestate was achieved. Furthermore, the process was stable. The pH value, suspended solids, and ammonium content remained stable at 8.5, 35%, and 3.8 g/kg, respectively. The acetic acid content was noted between almost 0.8 and over 1.1 g/kg, while the concentration of propionic acid was noted at maximum level of about 100 mg/kg. The AD conditions could positively affect the pathogen elimination. Based on these results it can be found that anaerobic digestion under thermophilic conditions results in high sanitation efficiency.

The Role of Pathogenic E. coli in Fresh Vegetables: Behavior, Contamination Factors, and Preventive Measures

Many raw vegetables, such as tomato, chili, onion, lettuce, arugula, spinach, and cilantro, are incorporated into fresh dishes including ready-to-eat salads and sauces. The consumption of these foods confers a high nutritional value to the human diet. However, the number of foodborne outbreaks associated with fresh produce has been increasing, with Escherichia coli being the most common pathogen associated with them. In humans, pathogenic E. coli strains cause diarrhea, hemorrhagic colitis, hemolytic uremic syndrome, and other indications. Vegetables can be contaminated with E. coli at any point from pre- to postharvest. This bacterium is able to survive in many environmental conditions due to a variety of mechanisms, such as adhesion to surfaces and internalization in fresh products, thereby limiting the usefulness of conventional processing and chemical sanitizing methods used by the food industry. The aim of this review is to provide a general description of the behavior and importance of pathogenic E. coli in ready-to-eat vegetable dishes. This information can contribute to the development of effective control measures for enhancing food safety.

An epidemiological investigation on occurrence of enterohemorrhagic Escherichia coli in raw milk

AIM

The aim of the present investigation was to study the epidemiology of enterohemorrhagic Escherichia coli (EHEC) in raw milk and molecular characterization of isolates using multiplex polymerase chain reaction (PCR).

MATERIALS AND METHODS

A total of 125 raw milk samples were subjected to isolation, identification, and confirmation of virulence-associated genes by multiplex PCR (mPCR). The samples were collected from a milk cooperative society of Thrissur district, Kerala. For further epidemiological investigation, samples such as dung (126), hair coat of cow (60), udder swab (60), udder wash (60), milking utensil wash (36), Milker's hand wash (36), water (36), soil (36), and feed (36) were collected from the households from which the raw milk tested positive for EHEC.

RESULTS

The occurrence of EHEC in individual raw milk samples was found to be 8.8%. The major source of contamination to raw milk was found to be dung (19.84%) followed by udder swab (16.67%), hair coat of cow (15%), Milker's hand and milking utensils and water (11.11% each), and udder wash and soil (8.33% each). For identification of virulence genes, all the isolates were subjected to mPCR, of 75 isolates 73.33% of isolates harbored stx 2 gene while 53.33, 36, and 36% of isolates were encoded by stx 1, eae A, and hly A genes, respectively. On epidemiological survey, the multiple risk factors accountable for occurrence of EHEC in raw milk were found to be the quality of water used, improper and inadequate udder preparation, unhygienic hands of Milker's, use of insufficiently cleaned milking utensils, and using common utensil for washings of udder and milking purposes.

CONCLUSION

The result of the present study signifies that raw milk was contaminated with EHEC and possesses a high public health threat. As dairy cattle and its environment serve as a potential niche for EHEC, hygienic milking practices should be adopted to curb the occurrence of EHEC in raw milk.

Sources and contamination routes of microbial pathogens to fresh produce during field cultivation: A review

Foodborne illness resulting from the consumption of contaminated fresh produce is a common phenomenon and has severe effects on human health together with severe economic and social impacts. The implications of foodborne diseases associated with fresh produce have urged research into the numerous ways and mechanisms through which pathogens may gain access to produce, thereby compromising microbiological safety. This review provides a background on the various sources and pathways through which pathogenic bacteria contaminate fresh produce; the survival and proliferation of pathogens on fresh produce while growing and potential methods to reduce microbial contamination before harvest. Some of the established bacterial contamination sources include contaminated manure, irrigation water, soil, livestock/ wildlife, and numerous factors influence the incidence, fate, transport, survival and proliferation of pathogens in the wide variety of sources where they are found. Once pathogenic bacteria have been introduced into the growing environment, they can colonize and persist on fresh produce using a variety of mechanisms. Overall, microbiological hazards are significant; therefore, ways to reduce sources of contamination and a deeper understanding of pathogen survival and growth on fresh produce in the field are required to reduce risk to human health and the associated economic consequences.

Fiber optic surface plasmon resonance sensor for detection of E. coli O157:H7 based on antimicrobial peptides and AgNPs-rGO

A fiber optic surface plasmon resonance (FOSPR) sensor was developed for detection of Escherichia coli O157:H7 (E. coli O157:H7) in water and juice, based on antimicrobial peptides (AMP), Magainin I, as recognition elements and silver nanoparticles-reduced graphene oxide (AgNPs-rGO) nanocomposites assisted signal amplification. The uniform AgNPs-rGO was fixed on the surface of optical fiber and covered with gold film. Not only was the SPR response greatly enhanced, but also the AgNPs was prevented from being oxidized. The FOSPR showed a sensitivity of about 1.5 times higher than that fabricated only with gold film. In the assay, Magainin I, immobilized on the surface of gold film, could specifically capture E. coli O157:H7, resulting in the wavelength shift of the SPR absorption peak. Under the optimized conditions, the SPR resonance wavelength exhibited a good linear relationship with natural logarithm of the target bacteria concentration in the range of 1.0 × 10³ to 5.0 × 10⁷ cfu/mL with the detection limit of 5.0 × 10² cfu/mL (S/N = 3). The FOSPR sensor showed good specificity for E. coli O157:H7 detection compared to other bacteria similar to the target bacterial species. Furthermore, the FOSPR sensor was successfully applied to the detection of E. coli O157:H7 in water, fruit and vegetable juice with the satisfactory recoveries of 88-110%. This assay for E. coli O157:H7 detection possesses high sensitivity, good selectivity, reproducibility and stability. In addition, the AMP based SPR biosensing methodology could be extended to detect a wide variety of foodborne pathogens. Therefore, the versatile method might become a potential alternative tool in food analysis and early clinical diagnosis.

Larval digestion of different manure types by the black soldier fly (Diptera: Stratiomyidae) impacts associated volatile emissions

Volatile emissions from decomposing animal waste are known environmental pollutants. The black soldier fly, Hermetia illucens (L.), is being evaluated for industrialization as a means to recycle wastes and produce protein for use as food and feed. We examined the ability of black soldier fly larvae to reduce odorous compounds associated with animal wastes. Black soldier fly larvae were reared under laboratory conditions on poultry, swine, and dairy manure at feed rates of 18.0 and 27.0 g every other day until 40% reached the prepupal stage. Volatile emissions were collected and analyzed from freshly thawed as well as the digested waste when 90% of the black soldier fly larvae reached the prepupal stage. Volatiles were also collected simultaneously from manure not inoculated with black soldier fly larvae (non-digested) and held under similar conditions. Manure samples were analyzed for relative amounts of nine select odorous volatile organic compounds: phenol, 4-methylphenol, indole, 3-methylindole, propanoic acid, 2-methylpropanoic acid, butanoic acid, 3-methylbutanoic acid and pentanoic acid. Black soldier fly larvae reduced emissions of all volatile organic compounds by 87% or greater. Complete reductions were observed for 2-methly propanoic acid in digested poultry manure, phenol, 4-methylphenol, indole and all five fatty acids in digested swine manure, and 4-methylphenol, indole, 3-methylindole and all five acids in digested dairy manure. This study is the first to identify volatile emissions from manure digested by black soldier fly larvae and compare to those found in non-digested manure. These data demonstrate additional benefits of using black soldier fly larvae as a cost-effective and environmentally friendly means of livestock manure management in comparison to current methods.

CAPSULE

Black soldier fly larvae are capable of altering the overall profile of volatile organic compounds and reducing levels of targeted odorous compounds in livestock manure.

The prevalence of Escherichia coli O157:H7 fecal shedding in feedlot pens is affected by the water-to-cattle ratio: A randomized controlled trial

Escherichia coli O157:H7 fecal shedding in feedlot cattle is common and is a public health concern due to the risk of foodborne transmission that can result in severe, or even fatal, disease in people. Despite a large body of research, few practical and cost-effective farm-level interventions have been identified. In this study, a randomized controlled trial was conducted to assess the effect of reducing the level of water in automatically refilling water-troughs on fecal shedding of E. coli O157:H7 in feedlot cattle. Pens in a feedlot in the Texas Panhandle were randomly allocated as control (total number: 17) or intervention (total number: 18) pens. Fecal samples (2,759 in total) were collected both at baseline and three weeks after the intervention, and tested for the presence of E. coli O157:H7 using immunomagnetic bead separation and selective culture. There was a strong statistical association between sampling date and the likelihood of a fecal sample testing positive for E. coli O157:H7. Pen was also a strong predictor of fecal prevalence. Despite accounting for this high level of clustering, a statistically significant association between reduced water levels in the trough and increased prevalence of E. coli O157:H7 in the feces was observed (Odds Ratio = 1.6; 95% Confidence Interval: 1.2–2.0; Likelihood Ratio Test: p = 0.02). This is the first time that such an association has been reported, and suggests that increasing water-trough levels may be effective in reducing shedding of E. coli O157:H7 in cattle feces, although further work would be needed to test this hypothesis. Controlling E. coli O157:H7 fecal shedding at the pre-harvest level may lead to a reduced burden of human foodborne illness attributed to this pathogen in beef.

Effect of Dairy Manure Storage Conditions on the Survival of E. coli O157:H7 and Listeria

Dairy manure is regularly applied to crop fields as a solid or liquid to improve the soil nutrient status. However, pathogens may survive during manure storage and enter the environment during application. In this study, three storage practices were evaluated to understand the survival patterns of O157:H7 and spp. in dairy manure using a culture-based approach. To replicate common farm manure storage techniques, solid manure was stacked as piles with periodic turning or as static piles without turning, whereas liquid manure (feces, urine, and water) was stored as a slurry in small tanks to simulate lagoon conditions. The and levels in the manure samples were determined for 29 wk. Results showed that there was an initial reduction in bacteria levels in the first month; however, both and managed to survive in the solid manure piles for the full study period. In slurry samples, was not detected after 14 wk, but survived until the end of the experiment at relatively lower levels than in the solid manure piles. Ambient weather and pile size were identified as the main reasons for bacteria survival during the course of the experiment. The outcome of this study is important in terms of understanding pathogen survival in manure piles and slurries prior to their application to crop fields.

Pathogen Decontamination of Food Crop Soil: A Review

The purpose of this review is to delineate means of decontaminating soil. This information might be used to mitigate soil-associated risks of foodborne pathogens. The majority of the research in the published literature involves inactivation of plant pathogens in soil, i.e., those pathogens harmful to fruit and vegetable production and ornamental plants. Very little has been published regarding the inactivation of foodborne human pathogens in crop soil. Nevertheless, because decontamination techniques for plant pathogens might also be useful methods for eliminating foodborne pathogens, this review also includes inactivation of plant pathogens, with appropriate discussion and comparisons, in the hopes that these methods may one day be validated against foodborne pathogens. Some of the major soil decontamination methods that have been investigated and are covered include chemical decontamination (chemigation), solarization, steaming, biofumigation, bacterial competitive exclusion, torch flaming, microwave treatment, and amendment with biochar. Other innovative means of inactivating foodborne pathogens in soils may be discovered and explored in the future, provided that these techniques are economically feasible in terms of chemicals, equipment, and labor. Food microbiology and food safety researchers should reach out to soil scientists and plant pathologists to create links where they do not currently exist and strengthen relationships where they do exist to take advantage of multidisciplinary skills. In time, agricultural output and the demand for fresh produce will increase. With advances in the sensitivity of pathogen testing and epidemiological tracebacks, the need to mitigate preharvest bacterial contamination of fresh produce will become paramount. Hence, soil decontamination technologies may become more economically feasible and practical in light of increasing the microbial safety of fresh produce.

Persistence of Indigenous Escherichia coli in Raw Bovine Manure-Amended Soil

The Food Safety Modernization Act attempts to reduce produce-related foodborne illness by using preventive rather than reactive measures. The goal of this research was to determine the persistence of manure-borne generic Escherichia coli under laboratory and field conditions. The population density of naturally occurring E. coli was ∼7.2 and 5.4 log CFU/10 g in pre- and postscreened manures, respectively. Postscreened (i.e. after the liquid manure has passed through a screen) manure was applied at light, medium, and heavy rates to fields in Live Oak and Citra, FL, during the fall and summer. Laboratory microcosms of the manure-amended soils (comparable to the field's heavy application rate of manure) from both locations were maintained at 20 and 30°C. Persistence of E. coli, moisture content, and pH were monitored until E. coli became unrecoverable. The longest E. coli persistence seen in field trails was during the summer and fall trials from Citra (heavy application) that terminated on day 112 and day 280, respectively. The rate of E. coli decay ranged from 0.02 to 0.04 log CFU per day across all manure application rates, seasons, and locations. In the microcosm studies, the E. coli became extinct on day 210 in the 30°C, whereas they became unrecoverable on day 420 in the 20°C microcosms. The relatively prolonged persistence of E. coli in the microcosms suggests that survival under laboratory conditions does not mimic real-world survival rates and may not be adequate for predicting E. coli persistence in the field. The persistence data also suggest that the risk from E. coli associated with new contamination events, such as wild life intrusion, runoff, or other vectors, may be greater than the risk associated with the long-term survival of manure-borne E. coli, although more work is needed to confirm this hypothesis.

Frequency and risk-factors analysis of Escherichia coli O157:H7 in Bali-cattle

Cattle are known as the main reservoir of zoonotic agents verocytotoxin-producing Escherichia coli. These bacteria are usually isolated from calves with diarrhea and/or mucus and blood. Tolerance of these agents to the environmental conditions will strengthen of their transmission among livestock. A total of 238 cattle fecal samples from four sub-districts in Badung, Bali were used in this study. Epidemiological data observed include cattle age, sex, cattle rearing system, the source of drinking water, weather, altitude, and type of cage floor, the cleanliness of cage floor, the slope of cage floor, and the level of cattle cleanliness. The study was initiated by culturing of samples onto eosin methylene blue agar, then Gram stained, and tested for indole, methyl-red, voges proskauer, and citrate, Potential E.coli isolates were then cultured onto sorbitol MacConkey agar, and further tested using O157 latex agglutination test and H7 antisera. Molecular identification was performed by analysis of the 16S rRNA gene, and epidemiological data was analyzed using STATA 12.0 software. The results showed, the prevalence of E. coli O157:H7 in cattle at Badung regency was 6.30% (15/238) covering four sub districts i.e. Petang, Abiansemal, Mengwi, and Kuta which their prevalence was 8.62%(5/58), 10%(6/60), 3.33%(2/60), and 3.33(2/60)%, respectively. The analysis of 16S rRNA gene confirmed of isolates as an E. coli O157:H7 strain with 99% similarities. Furthermore, the risk factors analysis showed that the slope of the cage floor has a highly significant effect (P<0.05) to the distribution of infection. Consequently, implementing this factor must be concerned in order to decrease of infection.

Reducing Foodborne Pathogen Persistence and Transmission in Animal Production Environments: Challenges and Opportunities

Preharvest strategies to reduce zoonotic pathogens in food animals are important components of the farm-to-table food safety continuum. The problem is complex; there are multiple pathogens of concern, multiple animal species under different production and management systems, and a variety of sources of pathogens, including other livestock and domestic animals, wild animals and birds, insects, water, and feed. Preharvest food safety research has identified a number of intervention strategies, including probiotics, direct-fed microbials, competitive exclusion cultures, vaccines, and bacteriophages, in addition to factors that can impact pathogens on-farm, such as seasonality, production systems, diet, and dietary additives. Moreover, this work has revealed both challenges and opportunities for reducing pathogens in food animals. Animals that shed high levels of pathogens and predominant pathogen strains that exhibit long-term persistence appear to play significant roles in maintaining the prevalence of pathogens in animals and their production environment. Continued investigation and advancements in sequencing and other technologies are expected to reveal the mechanisms that result in super-shedding and persistence, in addition to increasing the prospects for selection of pathogen-resistant food animals and understanding of the microbial ecology of the gastrointestinal tract with regard to zoonotic pathogen colonization. It is likely that this continued research will reveal other challenges, which may further indicate potential targets or critical control points for pathogen reduction in livestock. Additional benefits of the preharvest reduction of pathogens in food animals are the reduction of produce, water, and environmental contamination, and thereby lower risk for human illnesses linked to these sources.

Concentrations of Campylobacter spp., Escherichia coli, Enterococci, and Yersinia spp. in the Feces of Farmed Red Deer in New Zealand

Intensive deer farming can cause environmental issues, mainly by its impact on soils and water quality. In particular, there is a risk to the microbial quality of water, as high quantities of suspended sediment and fecal bacteria can enter into water systems. The feces of farmed red deer (, = 206) from Canterbury and Southland, New Zealand, were analyzed with regard to the presence of spp., , enterococci, and spp.. Enterococci and were isolated from all samples, with mean concentrations of 4.5 × 10 (95% CI 3.5 × 10, 5.6 10) and 1.3 × 10 (95% CI 1.1 × 10, 1.5 × 10) per gram of dry feces, respectively. spp. were isolated from 27 fecal samples, giving an overall prevalence of 13.1%. isolation rates were variable within and between regions (Canterbury 7.95% [95% CI 2-14%], Southland 16.95% [95% CI 10-24%]). Five out of 42 composite samples were positive for , and one sample for The overall prevalence ranges on a per-animal basis were therefore 2.43 to 11.17% and 0.49 to 2.91%, respectively. This study is the first to quantify the concentration of spp. present in healthy deer farmed in New Zealand. Deer feces are a potential source of human campylobacteriosis, with all genotypes isolated also previously observed among human cases. The fecal outputs from deer should be regarded as potentially pathogenic to humans and therefore be appropriately managed.

Current Interventions for Controlling Pathogenic Escherichia coli

This review examined scientific reports and articles published from 2007 to 2016 regarding the major environmental sources of pathogenic Escherichia coli and the routes by which they enter the human gastrointestinal tract. The literature describes novel techniques used to combat pathogenic E. coli transmitted to humans from livestock and agricultural products, food-contact surfaces in processing environments, and food products themselves. Although prevention before contamination is always the best "intervention," many studies aim to identify novel chemical, physical, and biological techniques that inactivate or eliminate pathogenic E. coli cells from breeding livestock, growing crops, and manufactured food products. Such intervention strategies target each stage of the food chain from the perspective of "Farm to Table food safety" and aim to manage major reservoirs of pathogenic E. coli throughout the entire process. Issues related to, and recent trends in, food production must address not only the safety of the food itself but also the safety of those who consume it. Thus, research aims to discover new "natural" antimicrobial agents and to develop "multiple hurdle technology" or other novel technologies that preserve food quality. In addition, this review examines the practical application of recent technologies from the perspective of product quality and safety. It provides comprehensive insight into intervention measures used to ensure food safety, specifically those aimed at pathogenic E. coli.

Dose-dependent fate of GFP-expressing Escherichia coli in the alimentary canal of adult house flies

The adult house fly Musca domestica (L.) (Diptera: Muscidae) can disseminate bacteria from microbe-rich substrates to areas in which humans and domesticated animals reside. Because bacterial abundance fluctuates widely across substrates, flies encounter and ingest varying amounts of bacteria. This study investigated the dose-dependent survival of bacteria in house flies. Flies were fed four different 'doses' of green fluorescent protein (GFP)-expressing Escherichia coli (GFP E. coli) (very low, low, medium, high) and survival was determined at 1, 4, 10 and 22 h post-ingestion by culture and epifluorescent microscopy. Over 22 h, the decline in GFP E. coli was significant in all treatments (P < 0.04) except the very low dose treatment (P = 0.235). Change in survival (ΔS) did not differ between flies fed low and very low doses of bacteria across all time-points, although ΔS in both treatments differed from that in flies fed high and medium doses of bacteria at several time-points. At 4, 10 and 22 h, GFP E. coli ΔS significantly differed between medium and high dose-fed flies. A threshold dose, above which bacteria are detected and destroyed by house flies, may exist and is likely to be immune-mediated. Understanding dose-dependent bacterial survival in flies can help in predicting bacteria transmission potential.

Rainfall-induced release of microbes from manure: model development, parameter estimation, and uncertainty evaluation on small plots

A series of simulated rainfall-runoff experiments with applications of different manure types (cattle solid pats, poultry dry litter, swine slurry) was conducted across four seasons on a field containing 36 plots (0.75 × 2 m each), resulting in 144 rainfall-runoff events. Simulating time-varying release of Escherichia coli, enterococci, and fecal coliforms from manures applied at typical agronomic rates evaluated the efficacy of the Bradford-Schijven model modified by adding terms for release efficiency and transportation loss. Two complementary, parallel approaches were used to calibrate the model and estimate microbial release parameters. The first was a four-step sequential procedure using the inverse model PEST, which provides appropriate initial parameter values. The second utilized a PEST/bootstrap procedure to estimate average parameters across plots, manure age, and microbe, and to provide parameter distributions. The experiment determined that manure age, microbe, and season had no clear relationship to the release curve. Cattle solid pats released microbes at a different, slower rate than did poultry dry litter or swine slurry, which had very similar release patterns. These findings were consistent with other published results for both bench- and field-scale, suggesting the modified Bradford-Schijven model can be applied to microbial release from manure.

Assessing the impacts of temperature and storage on Escherichia coli, Salmonella, and L. monocytogenes decay in dairy manure

Elevated levels of animal waste-borne pathogen in ambient water is a serious human health issue. Mitigating influx of pathogens from animal waste such as dairy manure to soil and water requires improving our existing knowledge of pathogen reductions in dairy manure treatment methods. This study was conducted to enhance the  understanding of human pathogen decay in liquid dairy manure in anaerobic (AN) and limited aerobic (LA) storage conditions. The decay of three pathogens (Escherichia coli, Salmonella spp., and Listeria monocytogenes) was assessed in bench-scale batch reactors fed with liquid slurry. A series of temperatures (30, 35, 42, and 50 °C) conditions were tested to determine the impacts of temperature on Escherichia coli, Salmonella, and L. monocytogenes decay in AN and LA conditions. Results showed prolonged survival of E. coli compared to Salmonella and L. monocytogenes in both LA and AN environments. Variations in survival among pathogens with temperature and environmental conditions (i.e., LA and AN) indicated the necessity of developing improved dairy manure waste treatment methods for controlling animal waste-borne pathogens. The results of this study will help in improving the current understanding of human pathogen decay in dairy manure for making informed decisions of animal manure treatment by stakeholders.

Effects of Cover Crop Species and Season on Population Dynamics of Escherichia coli and Listeria innocua in Soil

Cover crops provide several ecosystem services, but their impact on enteric bacterial survival remains unexplored. The influence of cover cropping on foodborne pathogen indicator bacteria was assessed in five cover crop/green manure systems: cereal rye, hairy vetch, crimson clover, hairy vetch-rye and crimson clover-rye mixtures, and bare ground. Cover crop plots were inoculated with Escherichia coli and Listeria innocua in the fall of 2013 and 2014 and tilled into the soil in the spring to form green manure. Soil samples were collected and the bacteria enumerated. Time was a factor for all bacterial populations studied in all fields (P < 0.001). E. coli levels declined when soil temperatures dipped to <5°C and were detected only sporadically the following spring. L. innocua diminished somewhat but persisted, independently of season. In an organic field, the cover crop was a factor for E. coli in year 1 (P = 0.004) and for L. innocua in year 2 (P = 0.011). In year 1, E. coli levels were highest in the rye and hairy vetch-rye plots. In year 2, L. innocua levels were higher in hairy vetch-rye (P = 0.01) and hairy vetch (P = 0.03) plots than in the rye plot. Bacterial populations grew (P < 0.05) or remained the same 4 weeks after green manure incorporation, although initial reductions in L. innocua numbers were observed after tilling (P < 0.05). Green manure type was a factor only for L. innocua abundance in a transitional field (P < 0.05). Overall, the impacts of cover crops/green manures on bacterial population dynamics in soil varied, being influenced by bacterial species, time from inoculation, soil temperature, rainfall, and tillage; this reveals the need for long-term studies.

Effects of Chicken Litter Storage Time and Ammonia Content on Thermal Resistance of Desiccation-Adapted Salmonella spp

Broiler chicken litter was kept as a stacked heap on a poultry farm, and samples were collected up to 9 months of storage. Chicken litter inoculated with desiccation-adapted Salmonella cells was heat-treated at 75, 80, 85, and 150°C. Salmonella populations decreased in all these samples during heat treatment, and the inactivation rates became lower in chicken litter when storage time was extended from 0 to 6 months. There was no significant difference (P > 0.05) in thermal resistance of Salmonella in 6- and 9-month litter samples, indicating that a threshold for thermal resistance was reached after 6 months. Overall, the thermal resistance of Salmonella in chicken litter was affected by the storage time of the litter. The changes in some chemical, physical, and microbiological properties during storage could possibly contribute to this difference. Moisture and ammonia could be two of the most significant factors influencing the thermal resistance of Salmonella cells in chicken litter. Our results emphasize the importance of adjusting time and temperature conditions for heat processing chicken litter when it is removed from the chicken house at different time intervals.

Prevalence of Escherichia coli O157:H7 in surface water near cattle feedlots

Between April 2009 and July 2011, 311 surface water samples in 48 cattle feedlots distributed in an area of about 67,000 km(2) were analyzed to examine the environmental dissemination of Escherichia coli O157:H7. Samples were taken inside and outside the pens, exposed and not exposed to runoff from corrals, near the feedlots. Two types of samples were defined: (1) exposed surface waters (ESW; n=251), downstream from cattle pens; and (2) nonexposed surface waters (NESW; n=60), upstream from cattle pens. By multiplex PCR, 177 (70.5%) ESW samples were rfb(O157)-positive, and 62 (24.7%) E. coli O157, and 32 (12.7%) Shiga toxin-producing E. coli (STEC) O157:H7 strains were isolated. In the NESW samples, 36 (60.0%) were rfb(O157)- positive, and 9 (15.0%) E. coli O157, and 6 (10.0%) STEC O157:H7 strains were isolated. These results showed that the environmental surface waters exposed to liquid discharges from intensive livestock operations tended to be contaminated with more STEC O157:H7 than NESW. However, no significant difference was found. This fact emphasizes the relevance of other horizontal routes of transmission, as the persistence of E. coli in the environment resulting from extensive livestock farming. By XbaI-PFGE, some patterns identified are included in the Argentine Database of E. coli O157, corresponding to strains isolated from hemolytic uremic syndrome and diarrhea cases, food, and animals, such as AREXHX01.0022, second prevalent pattern in Argentina, representing 5.5% of the total database. In the study area, characterized by the abundance of waterways, pathogens contained in feedlot runoff could reach recreational waters and also contaminate produce through irrigation, increasing the potential dissemination of STEC O157:H7 and the risk of human infections. The control of runoff systems from intensive livestock is necessary, but other alternatives should be explored to solve the problem of the presence of E. coli O157 in the aquatic rural environment.

Persistence of Pathogenic and Non-Pathogenic Escherichia coli Strains in Various Tropical Agricultural Soils of India

The persistence of Shiga-like toxin producing E. coli (STEC) strains in the agricultural soil creates serious threat to human health through fresh vegetables growing on them. However, the survival of STEC strains in Indian tropical soils is not yet understood thoroughly. Additionally how the survival of STEC strain in soil diverges with non-pathogenic and genetically modified E. coli strains is also not yet assessed. Hence in the present study, the survival pattern of STEC strain (O157-TNAU) was compared with non-pathogenic (MTCC433) and genetically modified (DH5α) strains on different tropical agricultural soils and on a vegetable growing medium, cocopeat under controlled condition. The survival pattern clearly discriminated DH5α from MTCC433 and O157-TNAU, which had shorter life (40 days) than those compared (60 days). Similarly, among the soils assessed, the red laterite and tropical latosol supported longer survival of O157-TNAU and MTCC433 as compared to wetland and black cotton soils. In cocopeat, O157 recorded significantly longer survival than other two strains. The survival data were successfully analyzed using Double-Weibull model and the modeling parameters were correlated with soil physico-chemical and biological properties using principal component analysis (PCA). The PCA of all the three strains revealed that pH, microbial biomass carbon, dehydrogenase activity and available N and P contents of the soil decided the survival of E. coli strains in those soils and cocopeat. The present research work suggests that the survival of O157 differs in tropical Indian soils due to varied physico-chemical and biological properties and the survival is much shorter than those reported in temperate soils. As the survival pattern of non-pathogenic strain, MTCC433 is similar to O157-TNAU in tropical soils, the former can be used as safe model organism for open field studies.

Characterization and survival of environmental Escherichia coli O26 isolates in ground beef and environmental samples

In addition to Escherichia coli O157:H7, shiga toxin-producing E. coli (STEC) O26 was added to the zero-tolerance adulterant list together with other 5 non-O157 STEC serogroups in 2012. Four farm O26 isolates were used in this study; they were obtained from a on-farm survey study conducted in Alabama. The presence of 3 major pathogenic genes (stx1, stx2, and eaeA) was determined through multiplex polymerase chain reaction (PCR). Two major pathogenic gene profiles were observed: 3 of the farm isolates contain only the eaeA gene whereas 1 farm isolate has both the eaeA and the stx1 genes. No significant difference was seen among the 4 farm isolates in the antibiotic resistance tests. To test their survival in ground beef and environmental samples, 2 inoculums were prepared and inoculated at various concentrations into samples of ground beef, bovine feces, bedding materials, and trough water. One inoculum was made of 3 farm isolates containing only the eaeA gene and another inoculum contained the isolate with both the eaeA and stx1 genes. Inoculated beef samples were stored at 4 °C for 10 d and the inoculated environmental samples were stored at ambient temperature for 30 d. Results showed that virulence gene profiles do not have an impact on O26's ability to survive in ground beef and in environment (P > 0.05). The inoculation levels, sample types as well as the storage times are the major factors that impact O26 survival (P < 0.05).

A systems analysis of irrigation water quality in an environmental assessment of an E. coli O157:H7 outbreak in the United States linked to iceberg lettuce

A foodborne Escherichia coli O157:H7 outbreak in December 2006 included 77 illnesses reported in Iowa and Minnesota. Epidemiologic investigations by health departments in those states and the U.S. Centers for Disease Control and Prevention (CDC) identified shredded iceberg lettuce (Lactuca sativa L.) as the vehicle of transmission. The U.S. Food and Drug Administration (FDA) and Minnesota and California public health agencies traced the lettuce to several growing regions in California based on information from a lettuce processor in Minnesota. Samples from an environmental investigation initiated by the California Food Emergency Response Team (CalFERT) revealed a genetic match between the outbreak strain and environmental samples from a single farm, leading to an in-depth systems-based analysis of the irrigation water system on that farm. This paper presents findings from that systems-based analysis, which assessed conditions on the farm potentially contributing to contamination of the lettuce. The farm had three sources of irrigation water: groundwater from onsite wells, surface water delivered by a water management agency and effluent from wastewater lagoons on nearby dairy farms. Wastewater effluent was blended with the other sources and used only to irrigate animal feed crops. However, water management on the farm, including control of wastewater blending, appeared to create potential for cross-contamination. Pressure gradients and lack of backflow measures in the irrigation system might have created conditions for cross-contamination of water used to irrigate lettuce. The irrigation network on the farm had evolved over time to meet various needs, without an overall analysis of how that evolution potentially created vulnerabilities to contamination of irrigation water. The type of systems analysis described here is one method for helping to ensure that such vulnerabilities are identified and addressed. A preventive, risk-based management approach, such as the Water Safety Plan process for drinking water, may also be useful in managing irrigation water quality.

Hygiene and Sanitation in Biogas Plants

The increasing number of agricultural biogas plants and higher amounts of digestate spread on agricultural land arouse a considerable interest in the hygiene situation of digested products. This chapter reviews the current knowledge on sanitation during anaerobic digestion and the hygienic status of digestate concerning a multitude of pathogens potentially compromising the health of humans, animals and plants. Physical, chemical and biological parameters influencing the efficiency of sanitation in anaerobic digestion are considered. The degree of germ reduction depends particularly on the resistance of the pathogen of concern, the processing conditions, the feedstock composition and the diligence of the operation management. Most scientific studies facing sanitation in biogas plants have provided data ascertaining reduction of pathogens by the biogas process. Some pathogens, however, are able to persist virtually unaffected due to the ability to build resistant permanent forms. As compared to the feedstock, the sanitary status of the digestate is thus improved or in the worst case, the sanitary quality remains almost unchanged. According to this, the spreading of digestate on agricultural area in accordance to current rules and best practice recommendations is considered to impose no additional risk for the health of humans, animals and plants.

A model for assessing mammal contribution of Escherichia coli to a Texas floodplain

Context Free-ranging mammals contribute to faecal pollution in United States water bodies. However, research into wildlife impact on water quality is dependent upon unreliable data (e.g. data uncertainty, unknown importance of parameters). Aims Our goal was to determine the potential impacts of common free-ranging mammal species and their management on Escherichia coli in the study floodplain. Our objectives for this research were to construct a model from study area- and literature-derived data, determine important species for E. coli deposition, and conduct sensitivity analyses on model parameters to focus future research efforts. Methods We constructed a model that incorporated parameters for four wildlife species known to contribute E. coli in central Texas: raccoons (Procyon lotor), white-tailed deer (Odocoileus virginianus), Virginia opossums (Didelphis virginiana), and wild pigs (Sus scrofa). These parameters were (1) population density estimates, (2) defaecation rates, (3) defaecation areas, (4) E. coli concentration in faecal material estimates, and (5) E. coli survival. We conducted sensitivity analyses on the model parameters to determine relative importance of each parameter and areas for additional study. Key results We found that adjustment of raccoon and Virginia opossum population densities had higher impacts on E. coli in the floodplain than similar changes in other species across all spatial and seasonal variations. We also found that the changes in E. coli survival, E. coli concentration in raccoon faecal material, and defaecation rates had the highest impacts on E. coli in the floodplain. Conclusions Our sensitivity analyses indicated that the largest impacts to projected E. coli loads were from changes in defaecation rates followed by E. coli concentration in faecal material and E. coli survival. Watershed planners, ranchers, and regulators must be cautioned that faecal deposition patterns are location specific and could significantly impact which species are considered the most important contributors. Implications Although all parameters require more research, we recommend that researchers determine defaecation rates for contributing species due to their relatively large impacts on E. coli in comparison to the other parameters. We also suggest additional research in free-ranging wildlife faecal morphology (form and structure) and area of deposition. Finally, species-specific E. coli survival studies for free-ranging wildlife should be conducted.

Escherichia coli survival in, and release from, white-tailed deer feces

White-tailed deer are an important reservoir for pathogens that can contribute a large portion of microbial pollution in fragmented agricultural and forest landscapes. The scarcity of experimental data on survival of microorganisms in and release from deer feces makes prediction of their fate and transport less reliable and development of efficient strategies for environment protection more difficult. The goal of this study was to estimate parameters for modeling Escherichia coli survival in and release from deer (Odocoileus virginianus) feces. Our objectives were as follows: (i) to measure survival of E. coli in deer pellets at different temperatures, (ii) to measure kinetics of E. coli release from deer pellets at different rainfall intensities, and (iii) to estimate parameters of models describing survival and release of microorganisms from deer feces. Laboratory experiments were conducted to study E. coli survival in deer pellets at three temperatures and to estimate parameters of Chick's exponential model with temperature correction based on the Arrhenius equation. Kinetics of E. coli release from deer pellets were measured at two rainfall intensities and used to derive the parameters of Bradford-Schijven model of bacterial release. The results showed that parameters of the survival and release models obtained for E. coli in this study substantially differed from those obtained by using other source materials, e.g., feces of domestic animals and manures. This emphasizes the necessity of comprehensive studies of survival of naturally occurring populations of microorganisms in and release from wildlife animal feces in order to achieve better predictions of microbial fate and transport in fragmented agricultural and forest landscapes.

Survival of Escherichia coli on strawberries grown under greenhouse conditions

Strawberries are soft fruit that are not recommended to have a post-harvest wash due to quality concerns. Escherichia coli O157:H7 has been linked to outbreaks with strawberries but little is known about the survival of E. coli during the growth cycle of strawberries. The survival of E. coli on strawberry plants during growing under greenhouses conditions was evaluated. Soil, leaves, and strawberries (if present) were artificially contaminated with an E. coli surrogate either at the time of planting, first runner removal (4 wk), second runner removal (8 wk), or one week prior to harvest. At harvest E. coli was recovered from the leaves, soil, and strawberries regardless of the contamination time. Time of contamination influenced (P < 0.05) numbers of viable E. coli on the plant. The highest survival of E. coli (P < 0.0001) was detected in soil that was contaminated at planting (4.27 log10 CFU g soil(-1)), whereas, the survival of E. coli was maximal at later contamination times (8 wk and 1 wk prior to harvest) for the leaves (4.40 and 4.68 log10 CFU g leaves(-1)) and strawberries (3.37 and 3.53 log10 CFU strawberry(-1)). Cross contamination from leaves to fruit was observed during this study, with the presence of E. coli on strawberries which had not been present at the time of contamination. These results indicate that good agricultural best practices to avoid contamination are necessary to minimize the risk of contamination of these popular fruit with enteric pathogens. Practices should include soil testing prior to harvest and avoiding contamination of the leaves.

[Survival of VTEC O157 and non-O157 in water troughs and bovine feces]

Verotoxin-producing Escherichia coli (VTEC) is the etiologic agent of hemolytic-uremic syndrome (HUS), which typically affects children ranging in age from six months to five years old. Transmission is produced by consumption of contaminated food, by direct contact with animals or the environment and from person to person. In previous studies we determined that the environment of a dairy farm is a non-animal reservoir; thus, we proposed to study the survival of 4 VTEC isolates (O20:H19; O91:H21; O157:H7 and O178:H19) in sterile water troughs and bovine feces by viable bacteria count and detection of virulence genes by PCR. It was demonstrated that the survival of different VTEC isolates (O157 and non-O157) varied in terms of their own characteristics as well as of the environmental conditions where they were found. The main differences between isolates were their survival time and the maximal counts reached. The competitive and adaptive characteristics of some isolates increase the infection risk for people that are visiting or working on a farm, as well as the risk for reinfection of the animals and food contamination.